Soory, misread your orinial post slightly.
Use the propper carbon, you don't want too much brain damage. It's been a while since I've done this as I use a z filter myself now. There are quite a few grades of carbon nowadays. I used to use one that you poured into the spirit and then left it to do its job for a week before filtering through the coffee paper. So you really don't need a fancy filter. The z filter is a quicker way of doing this. I still through the carbon into the spirit which sit in a 19l spring water bottle and usually leave it as such. I then rack off what I need from time to time and run this through the z filter for some extra polishing. I always cut the spirit to 40% before treating it with carbon and this also reduces issues with it reacting with anything.
If you want a cheap filter buy 19mm poly filter used for micro irrigation systems. You can cut circle filters from the coffee filter paper, fill the rest of the housing up with carbon and let the spirit drip through very slowly(as in overnight, tap only just on).
http://www.stillspirits.com/ is a good source of information if you have not already been there.